Acute lung injury (ALl) is a common and devastating illness that occurs in the context of sepsis and other systemic inflammatory disorders. Recent studies suggest that genetic variation in proteins of the inflammatory cascade may influence the incidence or outcome of sepsis. Proteases released from inflammatory cells are principal mediators of ALl, as is transforming growth factor-beta1 (TGF-B1). Thrombospondin 1 (TSP1) is a widely expressed matricellular protein responsible for extracellular activation of TGF-B1 and is also a potent inhibitor of elastase and metalloproteases. The TSP1 knockout mouse develops a diffuse pneumonitis as its principal phenotype. The evidence for TGF-B1 and protease effects as key upstream events promoting ALl, and the histologic similarities of the TSP1 knockout and ALl suggest a lung protective role for TSP1 during inflammation. Genetic variation in TSP1 and its functional consequences is thus of interest for the pathophysiology of ALl. In preliminary work we identified novel single nucleotide polymorphisms (SNP) in human TSP1 that appear more prevalent in ALl, some of which change TSP1 function. These SNP encode changes in amino acids and at regulatory sites within TSPI. We hypothesize that TSP1 genetic variants are more common in ALl patients and that they diminish TSP1 gene expression and function. We have 3 specific aims: 1) Complete a large association study of TSP1 genotype among sepsis, ALl, and healthy control groups to test the hypothesis that variant TSP1 SNP are more common in ALl and correlate with worse outcome; 2) Perform assays of promoter activity and transcription factor binding to test the hypothesis that variant SNP in regulatory sites decrease TSP1 promoter activity, alter transcription factor binding, and alter exon splicing; and 3) using genotype specific TSP1 protein test the hypothesis that TSP1 protein variants are less effective inhibitors of proteases and regulators of TGF-B1. This work will provide insight into the role of the biology of TSP1 and its common genetic variation as factors influencing ALl pathophysiology.